In conventional drilling systems, a drill string may include a series of connected drill rods. The drill rods may be assembled section-by-section to advance the drill string into a formation. In further detail, the drill string may be connected to a drill head or other driving mechanism configured to advance the drill string to a desired depth in the formation. The driving mechanism may, for example, advance the drill string until a trailing portion of the drill string is proximate an opening of a borehole formed by the drill string.
After the drill string is at a desired depth, a clamp (such as a foot clamp) may grasp the drill string, which may help prevent inadvertent loss of the drill string down the borehole. With the clamp grasping the drill string, the driving mechanism may be disconnected from the drill string. An additional drill rod may then be connected to the driving mechanism and to a drill rod that forms the trailing portion of the drill string. After such connection, the clamp's grasp on the drill string may be released, and the driving mechanism may advance the drill string further into the formation to a greater desired depth. This process of grasping the drill string, disconnecting the driving mechanism, connecting an additional drill rod, releasing the grasp, and advancing the drill string to a greater depth may be repeatedly performed to drill deeper and deeper into the formation.
In conventional drill rod clamps, the jaws of the clamps are moved to a closed position gripping the drill rod under the force of large a number of preloaded coiled springs or Belleville washers. To provide adequate drill gripping force to rotate the drill string in the case of the coiled springs, a large number of springs are required, e.g. some 22 coiled springs, which have a significant height. Similarly, with the Belleville washers, a large number of stacks of washers, e.g. 18 stacks, of heights comparable to the coiled springs are required. To accommodate the large number of springs or washer stacks conventional chucks are necessarily large, heavy and costly.
Alternative drill rod clamp designs typically use actuators to generate movement of the jaws of the clamp. However, these alternative designs often have a large profile comparable to that of clamps having coiled springs or Belleville washers. Further, actuated drill rod clamp designs often include external actuators that are prone to damage during use.
Still further, usage of existing drill rod clamps often leads to undesired dispersal of water, mud, and cuttings toward pistons acting to effect movement of the jaws of the clamps. Additionally, existing drill rod clamps are prone to jamming and damage due to their inability to adequately disperse mud and cuttings that are positioned above the jaws of the clamps.
Thus, there is a need in the pertinent art for drill rod clamp assemblies and methods that can address one or more of the above-described limitations.